A liquid crystal display used for personal computers, word processors, mobile phones and the like, and other various commercial displays are used in extremely wide ranging area. Transparent substrates of glass, plastic and the like are used in these displays and visual information such as substances, letters, figures and the like are recognized through these transparent substrates.
The practical problems of these displays include the deterioration of visibility due to the reflection of a display surface. That is, when a display is used in such environments that external light enters the display irrespective of from indoor or outdoor, visual information within the display becomes less visible because of reflection of incident light such as external light on the surface of the transparent substrate.
A method of preventing such reflection on a transparent substrate includes, for example, a method in which a coating layer having concavities and convexities is formed on the surface of a transparent substrate and external light is reflected diffusely by these concavities and convexities on the surface.
For example in Patent Document 1, there is disclosed an antireflection layer having concavities and convexities resulting from silica particles or agglomerated silica particles on its surface, which is obtained by mixing a silica dispersion into a silicate base coating agent prepared by a sol-gel method, applying the resulting mixture onto a glass substrate and baking it. And, in Patent Document 2, there is disclosed an antireflection layer which is formed by forming an intermediate layer based on a resin on a transparent base film and applying a coating solution containing organic ultra fine particles having a refractive index of 1.45 or less onto this intermediate layer and which has an outermost layer above which the surfaces of the organic ultra fine particles are exposed as concavities and convexities.
However, a method, in which concavities and convexities are formed on the surface of a transparent substrate and external light is reflected diffusely by these concavities and convexities, reduces apparent glare but does not reduce the whole quantity of reflected light, and this method has a problem that the antireflection film entirely looks whitish. Also, there was a problem that soil such as fingerprints, sebum, sweat and cosmetics is apt to adhere to the concavities and convexities at the surface and the adherent soil cannot be easily removed because of minute concavities and convexities.
On this problem, a method of forming an antireflection layer having a low refractive index on the surface of a transparent substrate is proposed. By forming the antireflection layer having a low refractive index on the surface of a transparent substrate, there are not problems of diffuse reflection of light and soil and the reflection on a transparent substrate can be prevented.
As such the antireflection layer having a low refractive index, layers comprising silicon base or fluorine base material have been used, but since these materials generally have poor adhesion to a transparent substrate, for example, antireflection films, in which a coating layer is formed on the transparent substrate using a coating agent obtained by dispersing particles having a low refractive index such as silica particles having a particle size of the order of nanometer, are attempted. For example, in Patent Document 3, there are disclosed a coating agent having a low refractive index in which hollow silica particles are mixed using an organic silicon compound polymer having a certain structure as a binder, and an antireflection film using the coating agent having a low refractive index.
However, since silica particles are less resistant to an alkali solution, a coating layer containing silica particles had a problem that the performance was deteriorated if a commercially available alkali detergent and the like were used for wiping out soil.
And when an inorganic base organic silicon compound polymer and the like are used as a binder component of a coating agent having low refractive index, the resulting coating layer was brittle and lacking in mechanical strength. On this problem, by using an organic binder component such as a transparent resin as a binder component of a coating agent having low refractive index, a coating layer which is superior in a film forming property and mechanical strength is obtained, however, since the silica particle has high dispersibility in an inorganic binder component such as an inorganic base organic silicon compound but has low dispersibility in an organic binder component such as a transparent resin, there was also a problem that it was difficult to use the transparent resin which was superior in a film forming property and mechanical strength as a binder due to the dispersibility in a resin as long as silica particle is used.
On this problem, it is also studied to use a hollow resin particle having a hollow rate of above a certain level as a particle having a low refractive index. Since the hollow resin particle has excellent alkali resistance and excellent dispersibility in a binder, it is expected that by use of such a hollow resin particle, reflection on the transparent substrate can be efficiently inhibited and an antireflection film having resistance to soil and cleaning and high mechanical strength can be attained.
As a method of producing such a hollow resin particle, there is disclosed, for example, in Patent Document 4 and Patent Document 5, a method of producing a polymer particle having a hollow in its inside by forming a core-shell type polymer by emulsion polymerization and treating it with a base, or a base and an acid. And, in Patent Document 6 and Patent Document 7, there is disclosed a method of producing a hollow resin particle by radical polymerization. And, in Patent Document 8, there is disclosed a method of producing a hollow resin particle by seed polymerization. Further, in Patent Document 9, Patent Document 10 and Patent Document 11, there is disclosed a method of producing a micro capsule having a shell obtained by an interfacial reaction.
However, though it is essential to achieve a high hollow rate in order to make the hollow resin particle have sufficiently low refractive index, all particles obtained by these methods had a particle size of the order of micrometer, and a hollow resin particle having a particle size of the order of nanometer, which attains enough high hollow rate to achieve a sufficient low refractive index, was not obtained.    Patent Document 1: Japanese Kokai Publication Hei-9-101518    Patent Document 2: Japanese Kokai Publication Hei-7-092305    Patent Document 3: Japanese Kokai Publication 2002-317152    Patent Document 4: Japanese Kokai Publication Hei-1-185311    Patent Document 5: Japanese Kokai Publication Hei-6-248012    Patent Document 6: Japanese Kokai Publication Hei-2-255704    Patent Document 7: Japanese Kokoku Publication Hei-5-040770    Patent Document 8: Japanese Kokai Publication Hei-8-20604    Patent Document 9: Japanese Kokai Publication Hei-8-48075    Patent Document 10: Japanese Kokai Publication Hei-8-131816    Patent Document 11: Japanese Kokai Publication Hei-10-24233